This invention relates to tools or measuring probes (hereinafter referred to collectively or individually as tools) for use with numerically controlled (NC) machine tools or with measuring machines.
Such machines have the capability of automatically substituting different types of tools in order to perform different machining or measuring operations on a workpiece. Each tool must therefore be capable of being releasably secured to the machine easily and quickly. Where a tool includes an electric circuit within its housing, a power supply has to be provided for the circuit, and this must be positioned either on the machine or within the tool and some form of releasable electrical connection has to be made between the tool and the machine. Physical electrical connections are not favored however because of the liklihood of corrosion due to the machine environment.
It is known, for example, from U.S. Pat. No. 4,145,816 to provide a battery within a tool for powering an electric circuit, and the electrical connection between the tool and the machine is made by an inductive connection. It is also known, for example, from UK Pat. No. 2,084,737 to use a battery in the tool to power an optical telemetry system for wirelessly transmitting signals from the tool to the machine.
The use of batteries however, has its drawbacks in that, at present, battery life is low, and the batteries require regular re-charging or replacement. Another problem is that ony a limited amount of power is available from the battery, particularly where the tool housing has to be small to enable it to fit into a limited amount of space. Thus for small tools requiring a relatively high power supply, a battery-powered tool may not be the best solution.